(1) Field of the Invention
This invention relates to a method of improving the quality of edge surfaces of cutting devices such as razors, kitchen, surgical and other knives, scissors, and mechanical cutting tools.
(2) Description of the Prior Art
Edge surfaces of cutting tools are required to have a high hardness.
Japanese Patent Publication Laid-Open Nos. 61-106767 and 62-382 have disclosed methods of improving the quality of edge surfaces, especially in terms of hardness. These methods are characterized in that vacuum deposition and ion irradiation are carried out simultaneously to the edge, thereby to form a mixture layer of the vacuum-deposited atoms and the irradiated ions.
However, these methods have the following problems.
1) The vacuum-deposited metal atoms are sputtered reversely by the irradiated ions, so as to lower the film forming speed. PA1 2) Since the ions bump into the edge (will be referred to as the base body, hereinafter) by a large acceleration voltage, the surface temperature of the base body is increased, which restricts the range of materials which can be used for the base body.
The material of the base body determines the characteristics of the film such as the crystallinity and the orientation, which can only be controlled in such a complicated and difficult way as changing the angle or the acceleration voltage for irradiating the ions.
With only keeping the temperature of the base body low being taken into consideration, a film of a highly hard material could be formed by vapor-depositing metal atoms which are in the state of gas in the room temperature or sputtering ions onto the base body. However, the film formed by such methods is adhered on the base body weakly enough to be peeled off or cracked easily.